Periodic voltage generator



Jan. 1a, 1938.

M. CAWEIN 2,105,902

PERIODIC VOLTAGE GENERATOR Filed Feb. 15, 1936 FIG. I. IO {I2 [l5 [l4[l5 CARRIER T VIDEO CATHODE FREQUENCY DETECTOR FREQUENCY RAY AMPLIFIER wAMPLIFIER TUBE l6 f PICTURE FREQUENCY. GENERATORR INVENTOR.

I MADISON C EIN I Q r I I11 ATTO NEY.

new 1.... 1a, was 2,105,902

UNITED STATES PATENT OF'FlCE rrmomo vouriioc csncaa'ron Madison Cawcin,Mnnhasw N. Y., assignor to multiple corporation, a corporation orDelaware Application February 15, 1936, Serial No. 54,022 12 Claims. (C250-36) This invention relates to the generation of periis, applied tothe plates with equal amplitudes odlc voltages of complex wave form,such as and opposite polarities, if maximum efliciency is saw-tooth andrelated forms, and to the utilitobe obtained. More particularly, bytilizi'ng two zation of such voltages, particularly for effectingbalanced deflecting voltages only one-half of the 5 cathode-ray scanningin television systems. voltage amplitude is required for each half ofthe According to present practice in television sysscanning voltagesupply, as in the case where tems, a carrier wave is transmitted,modulated by a n l un an s nn n v l is d. n picture or video-frequencysignals, corresponding 116K166 an Operating voltage may be used for h tothe varying values of light and shade in the generator which is of anamplitude of only onet itt picture, Scanning synchronizing imhalf thatwhich would be needed if a single un- 10 pulses are also transmitted,usually also as modubalanced Scanning Voltage were to be developedlationfrequencies impressed on the same tele- Furthermore, any electrostaticand magnetic disvision carrier as the video frequencies. A cathturbancesto which the voltage supply circuits ode-ray tube is employed at thereceiver, whercare subjected will be balanced out or neutralized in acathode ray. or electron beam is produced in these circuits also, whensuch a balanced ar-' 5 and focused upon a fluorescent screen. Voltagesfln is p y atvideo frequencies, derived from the received It is anobject of the present invention to carrier, are utilized to vary theintensity or the provide an improved generator for d veloping rayaccording to the signal amplitude. In order p riodic voltages which areof balanced, and h to effect scanning of the screen by the ray, sawp lyf wooth, w v form. wh ch are 20 tooth voltage or current waves aregenerated and of relatively high amplitudes, and which are utilized atthe receiver to produce, respectively, p cia ly sui l for e in a l v i nr ceiver electrostatic or magnetic fields of saw-tooth wave to effectscanning by the cathode y form which deflect the cathode ray, usuallyhori- A further object of this invention is to provide zontally for linescanning and vertically for pica generator of the character described,which is 25 ture scanning. The well-known rectilinear patrelativelysimple in its construction and operation. tern is thereby traced uponthe screen to repro- In accordance with the present invention, duce-thescene. The synchronizing impulses dethere is provided a periodic voltagegenerator rived from the carrier are utilized to control or whichincludes capacitance means, as for example operate the scanning wavegenerators so that the a condenser, and a source of direct current. A 30scanning actions at the receiver are maintained in pair of circuits isprovided for charging the caproper synchronism with the correspondingacpacitance means to opposite polarities from the tions at thetransmitter. direct-current source, and means-are provided In presentpractice, relatively high voltages are for controlling the circuits,periodically to charge employed for the electrodes of the cathode-raythe capacitance means alternately to opposite 5 tube, as ior focusingthe ray, and correspondingpolarities. One of the circuits includes twoimly high scanning voltages are, therefore, required. pedance means ofsubstantially equal values and It is, of course, essential that thesaw-tooth scansymmetrically disposed in the circuit for the ningvoltages be of such wave term as to effect periodic current th r in. Therm ym accurate linearityof trace and rapid retrace of rically disposedas used in this specification and 40 the scanning ray. Furthermore, itis highly dein the appended claims is intended to denote the sirablethat the scanning voltage generators be relationship wherebycorresponding portions of relatively simple in their construction andoperthe elements, in connection with which the term ation. is employed,are always at equal and opposite Because 01 inherent electrostatic andmagnetic periodic voltages with respect to ground. Suitdisturbances towhich the deflecting plates or a able means are provided for utilizingthe balanced cathode-ray tube are subjected in operation, it is periodicvoltages developed across the impedance desirable, it not necessary,that these plates he means. electrically balanced with respect toground, In the preierred embodiment of the invention, thereby toneutralize the effects of the disturbconstant-current devices, such aspentode tubes ances (which will then occur simultaneously and havingsuitable potentials applied to their elecin the same polarity on theopposite plates). trodes, are employed as the impedance means, With theplates so balanced" with respect to and vacuum tube conductances areemployed for ground, the deflecting voltages applied thereto controllingthe circuits periodically to effect the should also be balanced relativeto ground. that alternate charge of the capacitance means toaccelerating the action of the control tubes.

opposite polarities. Suitable means, as for example a regenerating tube,may be provided for of a cathode-ray tube, to eifect scanning by theray.

For a better understanding of the-present intion, while Fig. 2 is agraph of the balanced sawtooth voltages developed by the generator shownFig; 1.

eferring now particularly to the drawing, the

frequency or superheterodyne type,

includes, in cascade, an antenna and ground as lO-I I, acarrier-frequency amplifier I2, a detector l3, a video-frequencyamplifier I4 and a cathoderay tube l5. ere the receiver is of thesuperheterodyne type, the conventional oscilator l I,

will be hereinafter further described. The tube I5 is preferablyconventional in construction and operation.

Since the system shown in the drawing, thus far described, is, ingeneral,,wel-l understood in the art, a detailed explanation or itsgeneral nal from the amplifier i2 is delivered to the detector l3 inwhich are derived the video frequencies of modulation including thesynchronizing-i'requency components which are supplied to thevideo-frequency amplifier I 4, wherein they are amplified and thencesupplied,

in the picture-frequency generator l8 and line-frequency respectively,which generators are, as stated. conthesynchronizing-voltage; impulsesand are applied to the scanning elements of the cathode-ray tube toproduce magnetic and elecnate charges of the condenser to oppositepolarbattery [9 generator I1,

the screen and thereby reproduce the transmitted picture. Referring nowmore particularly to the portion of the system shown in the drawingwhich embodies the present invention, the voltage generator l1 comprisescapacitance means, more particularly a condenser III, and adirect-current source, such I9. by-Da Scd for periities. Specifically,one of the charging circuits of the condenser l8 includes thecontrolmeans,

biasing potential is applied the tube 2| from a tap on the battery It!by way of a resistor 24. The other charging circuit includes impedancemeans which, in the embodiment of the invention illus- Specifically, theconstant-current penand 33 are connected with their space-- currentpaths in series across the through the condenser 18 .and resistors 34and 35. Suitable potentials are supplied from the nitude as the voltage,of the source 19. the resultant balanced saw-tooth voltage is of anamplitude approaching twice that of the voltage of the source. It willbe understood,.however, that in place of the constant-current devices,

For regenerating the operation of the tubes 20 and 2|, there is provideda regenerating tube 25. The input circuit of the tu 251s eifecti'velycoupled to one of the charging 0 ts of the coni denser l8 and to thevideo-frequency amplifier ll 75 circuit. The junction of'theresistors 39and Ill the anode of the tube 23 and the other terminal,

through a coupling condenser 21, to the videofrequency amplifier H. Thecathode of the tube 25 is grounded and its control grid circuit includesa suitable biasing resistor 29. The anode of the tube 25 isconnected'directly to the control grid of the tube 2| and, by way of acoupling condenser 33, to the control grid of the Operating voltage issupplied from the battery l3, by'way of a resistor 3|, tube 25.

In order to utilize the periodic voltage thus developed, oppositeterminals of the condenser Il may be connected, by'way of couplingcondensers 31 and 33, directly to the scanning or deflecting elements ofthe cathode-ray tube i5. Preferably, a pair of serially-connectedresistors 39 and ill having their junction grounded for periodiccurrentsis connected across the load may be grounded, for direct current also,as shown, or may be maintained at any suitable direct voltage withreference to the operating voltages of the electrodes of the cathode-raytube.

In considering the operation of the generator ll shown in the drawing, asingle cycle will be described in detail from the point in the cycle atwhich the condenser I3 is charged to its maximum potential with itsupper plate, as shown in the drawing, positive. The tubes 32 and 33 areat all times conductive but the charging circuit of the condenserthrough these tubes is of high impedance, thereby limiting the rate ofcharge to a predetermined value. Under these conditions the condenser I3is gradually and linearly charged, so that the potential of its upperplate increases negatively and that of its lower plate, positivelythrough the circuit commencing at the positive terminal of the battery19 and-including the tube 32, resistor 34, condenser H, the tube 33 andresistor 35, to the other side of the battery. During this chargingoperation the potential of the cathode of the tube 32,and thus that ofthe anode or the tube increases positively, approaching that of thepositive terminal of the battery I9, Similarly, the potential of theanode of the tube 33,- and thus 'that of the cathode of thetube 20,increases negatively, approaching that of the negative terminal of thebattery I3. This charging action continues until suflicient voltages arebuilt up across the tubes 20 and 2| to break down the .tubes to initiatethe flow of current therethrough. The initial surge of current resultsin a voltage impulse across the resistor 22 which is applied negativelyto the control grid of the 'tube' 25 by way of the resistor 25 andcondenser 28, thereby reducing the conductance of this tube andproducing a positive voltage impulse across the resistor 3i. Thispositive voltage -is-instantaneously applied to the control grids of thetubes 20 and 2|,

the action of these tubes being thereby regenerated or accelerated, sothat "current builds up rapidly in the charging circuit which-includesthese tubes and charges the condenser I! to the opposite polarity. Asthe charge of the condenser ll approaches its-maximum value of theinitial 7 polarity, the charging current is reduced rapidly, withtheresult that the cathode of the tube 20 rapidly approaches thepotential of the positive terminal of the battery 19, while the cathodeof the tube 2| rapidly approaches the potential of to the anode of the 2I connected thereto,

the negative terminal of the battery i9. Under these conditions, thegrid of the tube 23 becomes negative with respect to its cathode by anamount approaching the voltage drop across the resistor 3 I while thegrid of the tube 20 becomes negative relative to its cathode by anamount approaching through the resistor 25. The tubes 23 and 2i are thusrendered-non-conductive and the charging of the condenser 13 to theopposite polarity is tial polarity, since the impedance of the circuitincluding the tubes 32 and 33 is very much higher than that of thecircuit including the tubes 20 and M.

The charging of the capacitance means or condenser IB alternately toopposite polarities is periodic and the action is synchronized by virtueof the synchronizing impulse voltages which are applied negatively tothe control grid of the tube 25 from the video-frequency amplifier, byway of the coupling condenser 21 and voltage divider 25. The circuitconstants are so selected that the voltage built up across the tubes 23and 2i during the trace is justshort of breaking down these tubes withnormal grid voltages applied. During this portion of the cycle the gridvoltage of the tube of" a negative synchronizing impulse, theconductanceof the tube 25 is suddenly decreased and its anode voltageraised. That is, the grid volt.- ages of the tubes 2il'and 2| areincreased positively to such a value that their existing anode voltagesare suflicient to break them down. The effectiveness, on the control ofthe tube 25, of the synchronizing voltage impulses from thevideo-frequency amplifier I4 and the voltage developed across resistor22 may be controlled simultaneously and in opposite senses by adjustmentof the tap on the voltage divider. Properly synchronized operation ofthe generator may thus be obtained. It will be understood that suitablediscriminating means will be included in the input circuit of thegenerator H5 or II, or both, to en.- sure that each is controlled onlyby its respective synchronizing impulses. Since the impedances of thetubes 32 and 33 are of substantially equal values, as are the resistors34 and 35. and since these elements are symmetrically disposed incurrent of the generator, the alternating voltage developed across thecondenser I8 is substantially balanced with respect to ground. Thisvoltage is impressed across the resistors 39 and 40 and is sent time andthe ordinates represent amplitude. Relative polarities are indicated asand and ground is indicated as 0. The received synchronizing voltageimpulsessupplied by thevideofrequency amplifier determine the frequencyat the generator, and the constants of the circuit determine theamplitude of the resultant voltages til 'the bias impressed thereon fromthe battery l3 1 their respective charging circuits for the periodicdeveloped. As clearly shown by the curves 4|,

and 42, the voltages which are developed are balanced relative toground.

While there has been described what at present is considered thepreferred embodiment of the invention, it will be obvious to thoseskilled in 1 the art that various changes and modifications may be madetherein without departing from the invention, and it is, therefore,aimed in the appended claims to cover all such changes and modificationsas fall within the true spirit and scope of the invention.

What is claimed is: g

1. A periodic voltage generator comprising capacitance means, adirect-current circuit, a pair 4 of circuits for charging saidcapacitance means to opposite polarities from said direct-currentcircuit, means for controlling said pair of circuits I periodically toeffect alternate charges of said capacitance means tooppositepolarities, one. of the circuits of said pair including two impedancemeans of substantially equal values and symmetrically disposed thereinfor the periodic current of said generator, and an output circuit inwhich the periodic voltages developed across said impedance means appearas balanced oppositely poled voltages. v

2. A periodic voltage generator comprising capacitance means, adirect-current circuit, a'pair of circuits for charging said capacitancemeans to opposite polarities from said direct-current circuit, means forcontrolling said pair of cir- I cuits periodically to eifect alternatecharges of means to opposite polarities from said direct-currentcircuit, means for controlling said pair of said capacitance means toopposite polarities, one of the circuits of said pair including twoimpedance means of substantially equal values and symmetrically disposedtherein for the periodic current of said generator, at least one of saidimpedance means being adapted to maintain the current in said circuitsubstantially constant, and an output circuit in which the periodicvoltages developed across said impedance means appear as balancedoppositely poled voltages.

3. A periodic voltage generator comprising capacitance means, adirect-current circuit, a pair of circuits for charging said capacitancemeans to opposite polarities from said direct-current cir cuit, meansfor controlling said pair of circuits periodically to,efiect'alternatecharges of said capacitance means to opposite polarities, one of thecircuits of said pair including two impedance means ofsubstantiallyequal values and symmetrically disposed therein for theperiodic current of said generator, each of said impedance meanscomprising a constant-currentdevicefor -maintaining the current in'saidcircuit substantially constant, and an output circuit in which theperiodic voltages developed across said impedance means appears asbalanced oppositely poled voltages.

'4. A periodic voltage generator comprising capacitance means, adirect-current circuit, a pair of circuits for charging said capacitancecircuits periodically to effect alternate charges of said capacitancemeans to opposite polarities, one ofthe circuits of said pair includingtwo impedance means of substantially equal values and symmetricallydisposed therein for the periodic current of said generator, each ofsaid impedance means including the space-current path of a pentode tube,means for applying potentials to the electrodes of said tubes wherebythey are eflective to maintain the current in saidcircuit which theperiodic voltages developed across said impedance means appear asbalanced oppositely poled voltages.

5. A periodic voltage generator comprising capacitance means, adirect-current circuit, a pair of circuits for charging said capacitancemeans to opposite polarities from said direct-current circuit, means forcontrolling said pair of circuits periodically to efi'ect alternatecharges of said capacitance means to opposite polarities, one of thecircuits of said pair including two unilaterally conductive impedancemeans of substantially equal impedance values, said impedance meansbeing symmetrically disposed for the periodic current of said generator,and an output circuit in which the periodic voltagm developed acrosssaid impedance means appear as balanced oppositely poled voltages.

6. A periodic voltage generator comprising capacitance means, adirect-current circuit, a

pair, two unilaterally conductive means symmetrically disposed thereinfor the periodic cur rent of said generator and connected with suchpolarity as to charge said capacitance means to a polarity oppo ite tothat of said first circuit, and

an output 0 cult in which the periodic voltages developed across saidimpedance means appear as balanced oppositely poled voltages.

7. A periodic voltage generator comprising capacitance means, adirect-current circuit, a pair of circuits 'for charging saidcapacitance means to opposite polarities from said directcurrentcircuit, means for controlling said pair of circuits periodically toeifect alternate charges of said capacitance means to oppositepolarities comprising, in one of the circuits of said pair,

-two impedance means of substantially equal 'values and symmetricallydisposed therein for the periodic current of said generator and, in theother of the circuits of said pair, the space-current paths of twovacuum tubes serially connected and symmetrically disposed therein forthe periodic current of said generator, and an output circuit in whichthe periodic voltages developed across said impedance means appear asbalanced oppositely poled voltages.

8. A periodic voltage generator comprising capacitance means, adirect-current circuit, a

pair of circuits for charging said capacitance means to opposite,polarities from said directcurrent circuit, means for controlling saidpair of circuits periodically to efiect alternate charges of saidcapacitance means to opposite polarities comprising, in one of thecircuits of said pair, two impedance means of substantially equal valuesand symmetrically disposed therein for theperiodic current of saidgenerator and, in the other of the circuits of said pair, the spacecurrent paths of two vacuum tubes each having a control electrode, saidtubes being serially connected and symmetrically disposed therein forthe periodic, current of said generator, means for energizing saidcontrol electrodes with synchronizing voltage impulses, and an outputcircapacitance means, a

cuit in which the periodic voltages developed across said impedancemeans appear as balanced oppositely poled voltages.

9. A periodic voltage generator comprising direct-current circuit, ,apair of circuits for charging said capacitance means to oppositepolarities from said direct-current circuit, means for controlling saidcircuits periodically to effect alternate charges of said capacitancemeans to opposite polarities comprising, in one of the circuits of saidpair, two impedance means of substantially equal valuw and symmetricallydisposed therein for the periodic current of said generator and, in theother of the circuits of said pair, the space-current paths of twovacuum tubes each having a controlelectrode, said tubes being seriallyconnected and symmetrically disposed therein for the periodic current ofsaid generator, means for energizing said control electrodes withsynchronizing voltage impulses, means'associated with said tubes forregenerating the action thereof, and an output circuit in which theperiodic voltages developed across said impedance means. a

10. A periodic voltage generator comprising capacitance means, adirect-current circuit, a 'pair of circuits for charging saidcapacitance means to opposite polarities from said directcurrentcircuit, means for controlling said pair or said capacitance means toopposite polarities comprising, in one of the circuits of said pair, twoimpedance means or substantially equal values and symmetrically disposedtherein for the periodic current of said. generator and, in

the other ofthe current paths oi two vacuum tubes each having a controlelectrode, said tubes being serially connected and symmetricallydisposed therein Patent No. 2,105,902.

of circuits periodically to effect alternate charges circuits of saidpair, the space-,

CERTIFICATE OF CORRECT-ION.

MADISON CAWEIN p for the periodic current of said generator, means forenergizing said control electrodes with synchronialng voltage impulses,a regenerating vacuum tube amplifier having its input circuit coupled toone or said circuits and itsv output circuit coupled to the controlelectrode of at least one of said charging tubes, and an output circuitin which the periodic voltages developed across said impedance means.

11. In a cathode-ray tube television receiver, a periodic voltagegenerator for developing scanning voltages for the tube of said receivercomprising capacitance means, a direct-current circuit, a pair ofcircuits for charging said capacitance'means toopposite polarities fromsaid direct-current circuit, means for controlling said pair of circuitsperiodically to effect alternate charges of said capacitance means toopposite polarities, one of the circuits of said pair including twoimpedance means of substantially equal values and symmetrically disposedtherein for the periodic current of said generator, and an outputcircuit in which the periodic voltages-developed across said impedancemeans.

12. An electric circuit arrangement for developing a periodic voltagebalanced relative to January- 18, 1958.

It is hereby certified that error appears in the printed specificationof the abovemumbered patent requiring correction as follows: Page secondcolumn line 21. claim', for the word "air" read pair; page 5, firstcolumn,

-line 8 cla1m9, after "said" insert pair of; 'line 2h, same claim,and'sec'onc' column, lines 9and 21 claims 10 and 11' respectively, after"means" and before th'e period insert'the words appear as balancedoppositely poled volt- Office.

( Seali Signed and sealed this 29th day of March, A. D; 19 58.

a Henry Van Arsdale,

- acting commissioner of Patents.

ages; and that the said- Letters Patent should be read with thesecorrections therein that thesame may conform to the record of the casein the Patent capacitance means, a

cuit in which the periodic voltages developed across said impedancemeans appear as balanced oppositely poled voltages.

9. A periodic voltage generator comprising direct-current circuit, ,apair of circuits for charging said capacitance means to oppositepolarities from said direct-current circuit, means for controlling saidcircuits periodically to effect alternate charges of said capacitancemeans to opposite polarities comprising, in one of the circuits of saidpair, two impedance means of substantially equal valuw and symmetricallydisposed therein for the periodic current of said generator and, in theother of the circuits of said pair, the space-current paths of twovacuum tubes each having a controlelectrode, said tubes being seriallyconnected and symmetrically disposed therein for the periodic current ofsaid generator, means for energizing said control electrodes withsynchronizing voltage impulses, means'associated with said tubes forregenerating the action thereof, and an output circuit in which theperiodic voltages developed across said impedance means. a

10. A periodic voltage generator comprising capacitance means, adirect-current circuit, a 'pair of circuits for charging saidcapacitance means to opposite polarities from said directcurrentcircuit, means for controlling said pair or said capacitance means toopposite polarities comprising, in one of the circuits of said pair, twoimpedance means or substantially equal values and symmetrically disposedtherein for the periodic current of said. generator and, in

the other ofthe current paths oi two vacuum tubes each having a controlelectrode, said tubes being serially connected and symmetricallydisposed therein Patent No. 2,105,902.

of circuits periodically to effect alternate charges circuits of saidpair, the space-,

CERTIFICATE OF c0RREcTIoN.-

MADISON CAWEIN p for the periodic current of said generator, means forenergizing said control electrodes with synchronialng voltage impulses,a regenerating vacuum tube amplifier having its input circuit coupled toone or said circuits and itsv output circuit coupled to the controlelectrode of at least one of said charging tubes, and an output circuitin which the periodic voltages developed across said impedance means.

11. In a cathode-ray tube television receiver, a periodic voltagegenerator for developing scanning voltages for the tube of said receivercomprising capacitance means, a direct-current circuit, a pair ofcircuits for charging said capacitance'means toopposite polarities fromsaid direct-current circuit, means for controlling said pair of circuitsperiodically to effect alternate charges of said capacitance means toopposite polarities, one of the circuits of said pair including twoimpedance means of substantially equal values and symmetrically disposedtherein for the periodic current of said generator, and an outputcircuit in which the periodic voltages-developed across said impedancemeans.

12. An electric circuit arrangement for developing a periodic voltagebalanced relative to January- 18, 1958.

It is hereby certified that error appears in the printed specificationof the abovemumbered patent requiring correction as follows: Page secondcolumn line 21. claim', for the word "air" read pair; page 5, firstcolumn,

-line 8 cla1m9, after "said" insert pair of; 'line 2h, same claim,and'sec'onc' column, lines 9and 21 claims 10 and 11' respectively, after"means" and before th'e period insert'the words appear as balancedoppositely poled volt- Office.

( Seali Signed and sealed this 29th day of March, A. D; 19 58.

a Henry Van Arsdale,

- acting commissioner of Patents.

ages; and that the said- Letters Patent should be read with thesecorrections therein that thesame may conform to the record of the casein the Patent

